Retrieving xml parts uing Linq to XML

This snippet of XML below is part of a much larger XML. I have tried over and over to get address line 1, 2,3 and City and State, postal code and country. I want to functionalize this so I can pick out those addresses based on InvoiceHeader id="XXXX" however I keep running into a wall. I have tried the following query below or something along the lines but I keep getting an error object reference not set to an instance of an object.

here is my query can someone please point out my obvious mistake.

 IEnumerable<string> partNos =
            from item in PurchaseOrderXml.Descendants("RemitTo").Descendants("Address")
            where (string)item.Attribute("id").Value == "23951768"
            select (string)item;



<Invoice>
    <InvoiceHeader id="23951768" status="InProcess">
        <InvoiceName />
        <InvoiceNumber>23951768</InvoiceNumber>
        <InvoiceDate>2014-09-26 00:00:00.0</InvoiceDate>
        <DueDate>2014-10-26 00:00:00.0</DueDate>
        <SupplierInvoiceNo>534254504</SupplierInvoiceNo>
        <InvoiceType>Invoice</InvoiceType>
        <RemitTo>
            <Address>
                <AddressLine lineNumber="1">P O BOX 535182</AddressLine>
                <AddressLine lineNumber="2" />
                <AddressLine lineNumber="3" />
                <City>ATLANTA</City>
                <State>GA</State>
                <PostalCode>303535182</PostalCode>
                <Country isoCountryCode="US">United States</Country>
            </Address>
        </RemitTo>
     </InvoiceHeader>
</Invoice>